墩顶水平冲击作用后钢筋混凝土桥墩剩余承载力研究

Research on residual bearing capacity of reinforced concrete bridge piers following horizontal impacts at pier top

采用凸形盖梁的城市高架桥在地震作用下,桥梁上、下部结构之间的异相位振动可能会导致主梁与盖梁之间的撞击。为研究钢筋混凝土(RC)桥墩在震致墩顶水平冲击作用下的动力行为及其剩余承载力,设计2个桥墩模型分别进行冲击试验和拟静力试验。此外,基于ANSYS/LS-DYNA软件对冲击试验和拟静力试验进行有限元仿真,探讨冲击质量和速度、桥墩轴压比、截面宽度和配筋率等参数对单次冲击后桥墩剩余承载力的影响。考虑到震致撞击可能是连续多次的,进一步考虑损伤的累积作用,分析桥墩在连续冲击后剩余承载力变化情况。研究结果表明:由于构件的振动,在1次冲击过程中,冲击锤与桥墩之间会出现多次接触和分离;单次冲击时,桥墩剩余承载力随冲击质量和速度增大而减小,随桥墩截面宽度和配筋率的增加而增大;多次连续冲击时,桥墩剩余承载力随累积冲击动能增加而减小,在所考虑的加载模式下,冲击后桥墩承载力降低19%~32%。

For urban viaducts using inverted T-shaped cap beams,seismic-induced out-of-phase vibration between bridge super-and substructures may lead to the impact between the girders and cap beams.To investigate the dynamic behavior and residual bearing capacity of reinforced concrete(RC) piers due to earthquake-induced horizontal impact at pier top,two pier models were designed and used in the impact test and quasi-static test.In addition,the impact and quasi-static tests were simulated by ANSYS/LS-DYNA.Based on the numerical model,the effects of impact mass and velocity,pier's axial compression ratio,section width and reinforcement ratio on the residual bearing capacity following an impact was discussed.Considering that the earthquake-induced impacts might be multiple,the residual bearing capacity of piers due to multiple impacts was analyzed,which considered cumulative damage to the piers.The results show that because of the vibration of the pier model,multiple contacts and separations between the impact hammer and specimen are found in an impact.When subjecting to a single impact,the residual bearing capacity of piers decreases with the impact mass and velocity but increases with the pier's section width and reinforcement ratio.In the case of subjecting to multiple impacts,the residual bearing capacity decreases with the increase of the cumulative kinetic energy acting on the pier.After the impacts considered in the study,the bearing capacity of piers can be reduced by 19%-32%.